This is an R21 application proposing to conduct a preliminary study on the relationship between autonomic stress-reactivity and pain sensitivity in patients with fibromyalgia syndrome (FMS). Although the exact pathphysiologic mechanisms of FMS are yet to be determined, FMS is generally considered as a disorder involving dysregulated central pain modulation. In addition, FMS seems to be associated with dysfunctional stress adaptation. Many FMS patients report that stress exacerbates their pain and symptoms. Research has suggested that autonomic dysregulation exists in FMS. FMS patients tend to exhibited blunted autonomic reactivity to noise, cold, and physical stressors. Research in cardiovascular and headache disorders, as well as animal/human laboratory studies, have demonstrated the antinociceptive effects of increased arousal, particularly baroreflex and occulosympathetic reactivity. These previous reports suggest that dysregulated autonomic functions in response to stressors play an important role in elevated pain sensitivity and other FMS symptoms. In the proposed study, we hypothesize that 1) FMS is associated with blunted sympathetic reactivity, 2) FMS is related to increased susceptibility to develop orthostatic intolerance, and 3) stress-induced analgesics are minimized in FMS. 30 FMS patients, 30 patients with temporomandibular disorder (TMD: localized pain control), and pain-free healthy subjects will undergo various stress tasks, orthostatic torelance test, and pain sensitivity test while blood pressure and pupil size are continuously measured. The levels of stress associated with tasks are relatively moderate (mental arithmetic, discussion of stressful experience), thereby allowing us to determine the importance of daily stressors patients report as an aggravating factor. Results from this study thus should provide initial evidence regarding the effects of stress-induced dysautonomia in FMS symptoms. Furthermore, the results of the study may provide an important avenue for improving those symptoms secondary to autonomic dysfunction.